An Analog-to-Digital Converter (ADC) is a common component in many semiconductor devices. An ADC operates by receiving an analog input voltage signal and converting this voltage signal into a digital voltage signal representation. Many different types of ADCs are available.
Microcontrollers have multiple ADCs embedded on the same semiconductor chip. These embedded ADCs have been tested during production by measuring characteristic curves in a manner involving lengthy measurements due to characteristic conversion curves being sampled several times and the high precision ADCs having long settling times. Also, ADCs having high precision require expensive, high precision Automatic Test Equipment (ATE) hardware with a large number of signals being routed between the ATE hardware and the semiconductor chip. Each of these factors has a negative impact on production cost.
Alternatively, ADCs have been tested during production using a servo loop to measure the ADC characteristic conversion curves. Measurement times remain approximately constant, and complexity is reduced as a voltage generator is replaced with a voltage measurement instrument. This servo loop technique is still limited, however, as the signals from the semiconductor chip still have to be routed to the voltage measurement instrument.